Bug 2297484 (CVE-2024-40900)

Summary: CVE-2024-40900 kernel: cachefiles: remove requests from xarray during flushing requests
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: dfreiber, drow, jburrell, vkumar
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: kernel 6.1.95, kernel 6.6.35, kernel 6.9.6, kernel 6.10-rc4 Doc Type: If docs needed, set a value
Doc Text:
A vulnerability was found in the Linux kernel's cachefiles component, during the flushing of requests, this issue arises when requests are not properly removed from the xarray, leading to a use-after-free condition where a request can be accessed after it has been freed.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Description OSIDB Bzimport 2024-07-12 13:25:04 UTC
In the Linux kernel, the following vulnerability has been resolved:

cachefiles: remove requests from xarray during flushing requests

Even with CACHEFILES_DEAD set, we can still read the requests, so in the
following concurrency the request may be used after it has been freed:

     mount  |   daemon_thread1    |    daemon_thread2
------------------------------------------------------------
 cachefiles_ondemand_init_object
  cachefiles_ondemand_send_req
   REQ_A = kzalloc(sizeof(*req) + data_len)
   wait_for_completion(&REQ_A->done)
            cachefiles_daemon_read
             cachefiles_ondemand_daemon_read
                                  // close dev fd
                                  cachefiles_flush_reqs
                                   complete(&REQ_A->done)
   kfree(REQ_A)
              xa_lock(&cache->reqs);
              cachefiles_ondemand_select_req
                req->msg.opcode != CACHEFILES_OP_READ
                // req use-after-free !!!
              xa_unlock(&cache->reqs);
                                   xa_destroy(&cache->reqs)

Hence remove requests from cache->reqs when flushing them to avoid
accessing freed requests.